Arrhythmias

Types of Arrhythmias

• Rapid Heart Rhythms
• Slow Heart Rhythms

Rapid Heart Rhythms

Supraventricular Tachycardia (SVT)
SVT is a series of very rapid heartbeats that begin in the heart's upper chambers. SVT may occur when an extra pathway of electrical conducting tissue exists in the atria, in the AV node or between the atria and ventricles.

Wolff-Parkinson-White (WPW) Syndrome
In WPW, an abnormal "bridge" of tissue connects the atria and ventricles. This extra pathway, called an accessory pathway, makes it possible for electrical impulses to travel from the atria to the ventricles without going through the AV node.

Because it is prone to conduct impulses rapidly, an accessory pathway may also allow extremely rapid, and potentially serious, rhythms to occur.

Ventricular Tachycardia (VT)
With VT, abnormal electrical pathways exist in the ventricles. If an electrical signal enters such a pathway, it may start traveling in a circular pattern. This may cause the ventricles to contract with each cycle, and may result in a rapid heartbeat.

VT may not to stop by itself and may require medication or an implantable device to terminate the rhythm. What's worse, it can sometimes deteriorate into ventricular fibrillation and cardiac arrest.

Ventricular Fibrillation
Ventricular fibrillation results when multiple sites in the ventricles fire impulses very rapidly and in uncoordinated fashion. As a result, the ventricles quiver and cease to pump blood effectively, therefore stopping the circulation of blood. Death follows within a few minutes, unless a normal rhythm is restored with emergency treatment.

Slow Heart Rhythms

Sick Sinus Syndrome
In this condition, the sinus node fails to perform its role as the heart's natural pacemaker. It may not send electrical signals often enough, may skip some signals, or may send too many signals all at once.

As a result, the heart may beat too slowly (sinus bradycardia), pause for too long (sinus pause), or may alternate between being too slow and too fast (bradycardia-tachycardia syndrome).

Heart Block
In heart block, there is an interruption of the pathway on which impulses travel to the ventricles. Heart block may result in a very slow, unreliable heartbeat.

Ways to Test for Arrhythmias

How Doctors Diagnose Arrhythmias
If your doctor suspects you have an arrhythmias, he or she may order one or more diagnostic tests to confirm an arrhythmia and determine whether it is causing your symptoms.

The electrocardiogram (ECG or EKG) is a simple test that records the electrical activity of your heart.

Holter monitoring is a continuous recording of the ECG, usually for 24 hours, while the patient goes about his or her usual daily activities.

If a Holter monitor is unrevealing, then an event recorder may be worn. This device can be worn over a period of days or weeks, and is used to record abnormal heart rhythms that occur infrequently. Implantable event recorders are now also available for patients with very infrequent and severe symptoms.

The exercise ECG test (or treadmill test) allows doctors to record the ECG during the stress of exercise.

Electrophysiology (EP) Study
EP studies are often recommended in people who have experienced life-threatening arrhythmias. Other likely candidates include people with persistent systems in whom suspected arrhythmias could not be detected by other means.